1. Field of the Invention
The present invention is generally related to the cooling arrangement for a marine propulsion system and, more particularly, to a method for conducting cooling water through the engine, through exhaust manifolds, and through a thermostat housing while maintaining a recirculating cooling water path through the engine block and cylinder heads.
2. Description of the Prior Art
Those skilled in the art of marine propulsion systems are aware of many different ways in which cooling water can be circulated through various heat producing components before being conducted back into a body of water from which it was drawn.
U.S. Pat. No. 4,991,546, which issued to Yoshimura on Feb. 12, 1991, describes a cooling device for a boat engine. A number of embodiments of cooling systems for internal combustion engines powering marine watercraft are described. The engine cooling jacket delivers its coolant to an exhaust manifold cooling jacket adjacent the inlet end of the exhaust manifold and coolant is delivered from the exhaust manifold cooling jacket to a further cooling jacket around the inlet portion of an exhaust elbow. In one of the embodiments, a closed cooling system is provided for the engine cooling jacket, exhaust manifold cooling jacket and the elbow cooling jacket. In another embodiment, the system discharges coolant back to the body of water in which the watercraft is operating through a further cooling jacket of the exhaust elbow that communicates with its discharge end.
U.S. Pat. No. 6,368,169, which issued to Jaeger on Apr. 9, 2002, discloses a marine engine cooling system with a siphon inhibiting device. The siphon inhibiting valve is provided for a marine engine cooling system. The purpose of the valve is to prevent the draining of the pump and outboard drive unit from creating a siphon effect that draws water from portions of the cooling system where heat producing components exist. The valve also allows intentional draining of the system when the vessel operator desires to accomplish this function. The valve incorporates a ball that is captivated within a cavity. If the ball is lighter than water, its buoyancy assists in the operation of the valve.
U.S. Pat. No. 6,379,201, which issued to Biggs et al. on Apr. 30, 2002, discloses a marine engine cooling system with a check valve to facilitate draining. The cooling system is provided with a valve in which a ball moves freely within a cavity formed within the valve. Pressurized water, from a sea pump, causes the ball to block fluid flow through the cavity and forces pumped water to flow through a preferred conduit which may include a heat exchanger. When the sea pump is inoperative, the ball moves downward within the cavity to unblock a drain passage and allow water to drain from the heat generating components of the marine engine.
U.S. Pat. No. 6,644,024, which issued to Powers et al. on Nov. 11, 2003, discloses an exhaust system for a marine engine. An exhaust system for a marine engine provides individual exhaust gas conduits that are maintained separately from water conduits until the individual exhaust gas conduits can be combined within a common exhaust gas conduit. This combination of exhaust gas streams allows the amplitude of negative pressure pulses to be damped, by combination with each other, prior to the mixing of cooling water with the exhaust gas streams. Later, the combined exhaust gas stream can be mixed with a combined water stream.
U.S. Pat. No. 6,672,919, which issued to Beson on Jan. 6, 2004, describes a temperature control system for a marine exhaust. The control system lowers flow of cooling water to the water jacket and exhaust gas conduit of the exhaust system at low engine speeds. The control system is typically activated at and below a predetermined engine speed. Once activated, the control system operates to reduce flow of cooling water to the exhaust system. The control can operate in an on/off mode, or can modulate rate of flow of water through the exhaust system, or both. However the water flow is limited, a predetermined minimum flow of cooling water is maintained through the exhaust system, at least either at periodic levels, or at a constant but lowered rate, to maintain cooling in the exhaust system on rubber components of the exhaust system.
U.S. Pat. No. 4,977,741, which issued to Lulloff et al. on Dec. 18, 1990, discloses a combination exhaust manifold and exhaust elbow for a marine propulsion system. The combined manifold and elbow for an internal combustion engine includes an exhaust cavity for receiving exhaust from the engine, an exhaust passage leading from the exhaust cavity, and an exhaust discharge outlet. A first water jacket is provided around the exhaust cavity and a second water jacket is provided around the exhaust discharge passage.
U.S. Pat. No. 5,109,668, which issued to Lindstedt on May 5, 1992, discloses a marine exhaust manifold and elbow. The exhaust assembly includes a manifold portion, an elbow portion, a water jacket portion, and exhaust runner walls, providing a smooth continuous transition of exhaust gas flow from intake exhaust passages in the manifold portion to transfer exhaust passages in the elbow portion around a bend to a discharge exhaust passage, minimizing turbulent flow of exhaust through the manifold portion and elbow portion.
U.S. Pat. No. 5,148,675, which issued to Inman on Sep. 22, 1992, describes a marine exhaust manifold and header pipe system. It is intended for a multi-cylinder internal combustion engine and it has a plurality of inlet ports which are connected via a cavity in the manifold to an outlet port formed in a face of the manifold. At least one septum member is disposed in the manifold to divide the cavity into at least two chambers with each of which are associated at least two inlet ports.
U.S. Pat. No. 6,290,558, which issued to Erickson on Sep. 18, 2001, discloses an exhaust elbow with a water trap for a marine propulsion system. The elbow is provided with a water trap section that defines a water collection cavity. Within the water trap section, a barrier extends downward into the water collection cavity to define first and second exhaust passages. When water begins to collect in the water collection cavity, the cross sectional area of the exhaust passage is reduced and the velocity of exhaust gases passing through the exhaust passage is increased. The water collection cavity is shaped to be easily cleared when exhaust gas pressure increases as the engine speed increases.
U.S. Pat. No. 6,582,263, which issued to Jaeger et al. on Jun. 24, 2003, discloses a marine exhaust elbow structure with enhanced water drain capability. The elbow for a marine propulsion system is provided with a stainless steel tube within a water outlet opening to assure that a drain opening remains open even when the exhaust elbow is exposed to a corrosive atmosphere. Since cast iron tends to expand in volume as a result of corrosion of its surface areas, water outlet openings intended to perform a draining function can be partially or fully closed as a result of corrosion. The insertion of a stainless steel tube in one or more water outlet openings of an exhaust elbow assures that an internal water cavity of the elbow can be drained when the associated internal combustion engine is turned off, thereby minimizing the possibility of freeze damage to the exhaust components.
U.S. Pat. No. 6,652,337, which issued to Logan et al. on Nov. 25, 2003, discloses an exhaust system for a marine propulsion engine. It provides a relationship between the exhaust passages and coolant passages of the exhaust manifold and exhaust elbow which serves to maintain the joint of the exhaust passage at a higher temperature than would be possible with known exhaust manifolds and exhaust elbows. By providing a space between surfaces of a raised exhaust portion of the components and surfaces of the raised coolant portions of the components, leakage from the coolant conduits to the exhaust cavities is avoided.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In known cooling systems for marine propulsion devices, the coordination of cooling water flow between the engine block, cylinder head, and exhaust components, such as the exhaust manifolds and exhaust elbows, could allow unreliable cooling water flow to create hot spots in the exhaust components. During initial starting of the engine of a marine propulsion system, before the thermostat begins to open for the purpose of purging hot water from the engine, the exhaust manifolds and exhaust elbows are typically dependent on a bleed water flow to provide cooling. As these components achieve higher temperatures, typically before the engine itself achieves sufficient temperatures to open the thermostat control system, the flow of water through the exhaust manifolds and exhaust elbows can be insufficient to provide uniform cooling. In addition, known systems do not always provide a completely filled cooling water jacket around the exhaust manifolds.
It would therefore be significantly beneficial if a cooling water system could be provided for a marine propulsion system that maintains a filled cooling water jacket for both exhaust manifolds. It would also be beneficial if the pressure within those exhaust manifold cooling jackets could be maintained at an elevated magnitude to discourage boiling of the cooling water as it passes through the exhaust manifold cooling jackets. It would also be beneficial if a means could be provided to more rapidly increase the temperature flowing through the engine block and cylinder heads in order to achieve more efficient operation immediately after startup of the engine.
If a stabilized and more uniform temperature of the cooling water can be created and maintained throughout the cooling passages of the engine block and cylinder heads and the cooling jackets of the exhaust manifolds, condensation can be reduced and the efficiency of the engine operation can be improved.